Why isn't 3 phase available for homes???

[Kyle_in_Tex]

I hope to get some people here who know about electricity and can give me some good answers.
First to preface, everyone is spending countless bucks improving solar power, wind power, wave power you name it power.

From my pea sized knowledge of electicity, I know that 3 phase motors are somewhat more efficient. My buddy was telling me about delta Y type wiring methods and that with 3 phase a motor can use as little as 1/3 the amps. He also says the same can be said for electric water heating and home heating. All this can be done with 1 more leg ran to the home plus a different type of transformer? What gives, no rocket science needed, just not yet common easy to make 3 phase equipment.

He also said that the city of Austin had a round table discussion (between the power company and some electricians) back in the 70's about ways to save energy. He said this idea was presented and many electricians agreed but the idea was shelved he guessed by the power company "because they want to sell electricity". I said what about all the rebates and incentives they offer to reduce consumption? He says they do that to keep the greenies off their backs...

He said the whole house could be converted but the confusion of types of bulbs etc would be a hassle. I asked "Why don't they make it where hard wired stuff is 3 phase?" He said it can be done with money. AC, hot water, heating, dishwasher and oven is where he'd start. He says Europe is somewhat like this.
Is he right about most of this stuff? I know in the south, our cooling bills are really high and if a 3 phase AC unit could run on 33% of the electricity, I know I'd save about $70 a month on just AC.

 

[tommu56]

Kyle_in_Te

the basics is a Watt is a watt no mater the power and thats how people are billed for lighting and such it wouldn't change mutch.

the only things in a house that that might make since to be 3 phase are large loads like hvac equipment and range and the dryer

they do have 120v 208 3 phase for a compromise between the 120- 220 single phase and 3 phase

look at the chart below

one horse motor 120v 16.amps on 2 wires

same on 3 phase 7.2 amps a little over 1/2 don't forget you now need 3 wires and ground and add another pole to each controller (contactor or thermostat) all adding to cost and you can actually run it on 12 gauge wire you cant go much smaller when you get in to larger loads the wiring is larger and thats wee savings comes in.


HP
110-120V 220-240V 440-480V 550-600V
1ﾘ 3ﾘ 1ﾘ 3ﾘ 1ﾘ 3ﾘ 1ﾘ 3ﾘ
1/4 5.8 - 2.9 - - - - -
1/3 7.2 - 3.6 - - - - -
1/2 9.8 4.0 4.9 2.0 2.5 1.0 2.0 0.8
3/4 13.8 5.6 6.9 2.8 3.5 1.4 2.8 1.1
1 16.0 7.2 8.0 3.6 4.0 1.8 3.2 1.4


tom

 

[rox]

We do have 3 phase power in our pump house. Plus the voltage is really high I think 340 volts. i was taken to the pump house and taught all about it so that i never accidently electrocute myself. We have a big pump for 12 acres of irrigation lines that go up steep hillsides. of course we do run 220volts in the homes here so we are always careful about electrical risks. neither hubby nor myself would ever touch any electrical work here that is for sure.

 

[DieselPower]

The main advantage of 3 phase is in electric motors. They run more efficiently using 3 phase. There's no real advantage to using it in a house. Cost me around $14K to have it installed in the garage/shop a couple of years ago so I have it on my property and I still have no use for it in the house. I only have it to run my machine shop equipment.

 

[BobRip]

Kyle_in_Te

the basics is a Watt is a watt no mater the power and thats how people are billed for lighting and such it wouldn't change mutch.

the only things in a house that that might make since to be 3 phase are large loads like hvac equipment and range and the dryer

they do have 120v 208 3 phase for a compromise between the 120- 220 single phase and 3 phase

look at the chart below

one horse motor 120v 16.amps on 2 wires

same on 3 phase 7.2 amps a little over 1/2 don't forget you now need 3 wires and ground and add another pole to each controller (contactor or thermostat) all adding to cost and you can actually run it on 12 gauge wire you cant go much smaller when you get in to larger loads the wiring is larger and thats wee savings comes in.


HP
110-120V 220-240V 440-480V 550-600V
1ﾘ 3ﾘ 1ﾘ 3ﾘ 1ﾘ 3ﾘ 1ﾘ 3ﾘ
1/4 5.8 - 2.9 - - - - -
1/3 7.2 - 3.6 - - - - -
1/2 9.8 4.0 4.9 2.0 2.5 1.0 2.0 0.8
3/4 13.8 5.6 6.9 2.8 3.5 1.4 2.8 1.1
1 16.0 7.2 8.0 3.6 4.0 1.8 3.2 1.4


tom

I agree with Tom. There would be a little savings in energy, but the equipment cost more. Most people won't even buy the more efficient 220 volt single phase HVAC units, much less go for the three phase. Most people don't even have compact florescent bulbs, which save 2/3 on energy cost. There are many things that could be done easier and cheaper to save energy.

It is nice for large shop equipment, but at homes this is not usually run many hours a day.

 

[shimp]

u can buy a 3 phase converter

 

[kenmac]

I agree with Tom. There would be a little savings in energy, but the equipment cost more. Most people won't even buy the more efficient 220 volt single phase HVAC units, much less go for the three phase.


you are soooo right MR Bob
Folkes cry when I give them prices for 220 hvac motors, compressors. I can't think of what I would hear if I priced 3 phase stuff (equip/parts) for the home owner.

Besides , they would shoot their eyes out

 

[DieselPower]

u can buy a 3 phase converter

They completely defeat the reason for having 3 phase in the first place. Phase converters gobble up quite a bit of power.

 

[Tig]

Power is current multiplied by voltage. In it's simplest form the following example applies.
3 amp x 110V = 330 Watts
1 amp x (3 phase x 110V) = 330 Watts
So in my example the three phase load used 1/3 the Amps but still uses the same power.
Most loads will fit this example but as mentioned previously motors are one exception.

 

[EastTexFrank]

We are one of the few houses that have 3-phase in the county, or so the power company told me. They wanted to take it away from us on their last "upgrade" but backed off when I told them that they were welcome to do do so as long as they replaced my A/C and well pump which both use 3-phase. I'm not sure what all the advantages are but both systems have run without incident for the last 30 years in the case of the A/C and 10 years for the well pump. I think that is the main advantage right there, electric motors just last a lot longer on 3-phase, run more efficiently and therefore are cheaper but I think it is only noticible on motors that gobble up power.

 

[kossetx]

I have 3phase at my house here in houston, but it isn't used. the cost of equipment made me buy 1phase.

 

[texbaylea]

We had 3 phase at our home in Dickinson. The house was very near a school so it was available at the pole, just had to add a second transformer. The only 3 phase equipment was the A/C units, Lennox, by the way. This was the early 70s and the price delta was only about 12% as I remember. Those units ran for more than 25 years. They were due for replacement at the time we sold primarily because of corrosion, mainly on the coils. They had been submerged in the flood of "79 but I washed them out and flooded them with WD-40 to dry them out and they went to working again. Did have to replace the contactors within a few months. I did the same with all the major appliances and they continued to work for several years.

Vernon

 

[dubba]

In my area most of the savings from using 3 phase on larger motors is because of the way the electric company bills business accounts.

We pay for usage & peak demand. By using 3 phase equipment the usage stays approx the same but the demand per input is lower. The current combined demand charge in my area is $6.88 per highest average KW demand.

So from tommu56's example on a motor run for 1 hour continuously-

one horse motor 120v 16.amps = $13.21 demand charge

same on 3 phase 7.2 amps = $5.94

 

[BillyP]

In my area most of the savings from using 3 phase on larger motors is because of the way the electric company bills business accounts.

We pay for usage & peak demand. By using 3 phase equipment the usage stays approx the same but the demand per input is lower. The current combined demand charge in my area is $6.88 per highest average KW demand.

So from tommu56's example on a motor run for 1 hour continuously-

one horse motor 120v 16.amps = $13.21 demand charge

same on 3 phase 7.2 amps = $5.94

I don't know a thing about 3 phase so excuse my ignorance.

But this one horse motor that's pulling 16 amps would be pulling 16 amps if it were wired for 240.

How could a 3 phase one horse motor only pull 7.2 amps?

 

[tallyho8]

I don't know a thing about 3 phase so excuse my ignorance.
But this one horse motor that's pulling 16 amps would be pulling 16 amps if it were wired for 240. How could a 3 phase one horse motor only pull 7.2 amps?

If a 110v motor pulls 16 amps then that same hp motor running on 220v would pull 8 amps. They would both use the same number of watts.

The difference is that a 110v line has one 110v line and a neutral and pulls 16 amps on that one line.
The 220v line is actually two 110 volt lines in different phases and the motor pulls 8 amps on each line.
The 3 phase uses 3 lines in different phases. Now, someone explain the way to figure the amps on 3 phase to us.

 

[BillyP]

The difference is that a 110v line has one 110v line and a neutral and pulls 16 amps on that one line.
The 220v line is actually two 110 volt lines in different phases and the motor pulls 8 amps on each line.
The 3 phase uses 3 lines in different phases. Now, someone explain the way to figure the amps on 3 phase to us.

Yes I understand the amp draw...

120 volt motor = 16 amps on line 1

240 volt motor = 8 amps on both line 1 and 2 which = 16 amps.

What I don't get is how a 3 phase motor can pull less amps through the meter.

Is it as simple as wire size and voltage drop?

 

[caver]

Three phase

A = Kva x 1000
1.73 X E

 

[tallyho8]

Yes I understand the amp draw...120 volt motor = 16 amps on line 1 240 volt motor = 8 amps on both line 1 and 2 which = 16 amps. What I don't get is how a 3 phase motor can pull less amps through the meter. Is it as simple as wire size and voltage drop?

I don't believe that 3 phase pulls less amps through the meter, just less amps on each line. But your electric meter measures the electricity you use in watts, not in amps. Since your watts are the same, your electric bill would be the same for residential use.

For business usemost utility companies charge by demand also. Your demand charge is figured by the highest amount of killowatts or amps, depending on your utility company, that you use in a certain period of time. If you have a high demand for only one minute, the utility company can put a surcharge on your bill for demand for many months.

As an example of their demand charges, I owned an air conditioning company that I closed every winter for 3 months and only used a night light and a burglar alarm. My bill was usually only $25 a month minumum during those 3 months. One 4th of July we had a shindig and had 4 people come in campers and used my electricity for their air conditioners in addition to the amount I was regularly using. Though my bill was only about $15 more that month than usual for the campers, it raised my demand and surcharge so that during the winter months when I was closed my minumum bill went up to $50 per month. So those campers who only used $15 in electricity raised my bill over $90 that year.

And, no, I have not figured out how 3 phase would reduce a residential electric bill and am waiting to see if anyone can explain it in a way simple enough for me to understand it.

 

[BobRip]

Yes I understand the amp draw...

120 volt motor = 16 amps on line 1

240 volt motor = 8 amps on both line 1 and 2 which = 16 amps.

What I don't get is how a 3 phase motor can pull less amps through the meter.

Is it as simple as wire size and voltage drop?

There is current flowing through 3 wires instead of just 2. So for the same power and same voltage the current is less. The current in each leg is 120 degrees out of phase with the other two wires. I suggest you do a search on 3 phase power and read up. It's not real complex, but it's been 30 years since I studied it.

The life of the three phase motors is longer mostly because there are no starting capacitors or relays. These tend to fail. Parts that are not in a product cannot fail and cause problems.

 

[SpringHollow]

In this area, the meters used to just measure the amount of amps being pulled through the leg with the most amps. So if you had only an air conditioner running, the same cooling capacity would cost you half as much to run on a 220V unit versus a 110 V unit. In reality, many things are on at once so that the difference between the two legs usually is not real large unless someone put all of the high demand items on one leg. A good electrician would try to balance the load between the legs by moving circuits. This was done to even out the demand on the bus of the panel and to save on electrical costs.

I do not know if the newer meters work the same way now or not.

Ken